In addition to antiperspirant active ingredients, anhydrous antiperspirant suspensions that are sprayable using a propellant typically contain at least one cosmetic oil as a carrier for the particulate antiperspirant active ingredient. The suspensions are packaged in a pressure-resistant container, usually a can of tin plate or aluminum, which is lacquered on the inside, together with a liquefied hydrocarbon, such as n-butane, iso-butane and/or propane, as propellant. Before using the spray valve, during which propellant and a proportion of the suspension is released, the container must first be shaken sufficiently to mix in the antiperspirant active ingredient which has settled out. In order to prevent the suspended antiperspirant active ingredient from immediately settling back out, conventional commercial suspensions contain a suspending agent such as hydrophobically modified hectorites, some examples of which may be obtained under the trade names Bentone Gel or Bentone Powder from the companies Rheox and Elementis Specialties.
In conventional commercial sprays, the antiperspirant active ingredient suspended in the anhydrous carrier is covered with a layer of oil. During and after application onto the skin, this oil layer is favorable for the spray pattern. In other words, the active ingredient is not excessively atomized, but instead arrives in a targeted manner on the skin; the oil layer moreover ensures a certain level of adhesion of the pulverulent antiperspirant active ingredient to the skin. This oil layer may, however, delay the release of the antiperspirant active ingredient in its active water-soluble form. In particular, relatively non-polar oils and/or oils with a low solubility parameter contribute to delaying active ingredient release.
Attempts by the present applicant to replace the relatively non-polar oils and/or oils with a low solubility parameter to the greatest possible extent with polar oils and/or oils with a higher solubility parameter have not been met with much success; once the polar oils and/or oils with a higher solubility parameter constituted at least 50 wt. % of the entire carrier oil (excluding propellant), the product was discharged non-uniformly from the spray can and the spray pattern obtained was unsuitable for the intended application.
Cyclomethicone is already known in the prior art as a highly suitable carrier oil for antiperspirant sprays. Despite its low solubility parameter, very satisfactory release of the antiperspirant active ingredient is achieved with cyclomethicone, since this oil has a relatively high volatility and thus does not excessively block the antiperspirant active ingredient.
Due to cyclomethicone's persistence, its use should as far as possible be avoided. It is therefore desirable to formulate anhydrous antiperspirant compositions which exhibit improved active ingredient release of the antiperspirant active ingredient while dispensing to the greatest possible extent with the use of cyclomethicone.
Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the background of the invention.